A Microchip for Continuous-Flow, Magnetically Controlled Capture and Separation of Microparticles

This paper presents a novel microfluidic chip that exploits magnetic manipulation for integrated capture and separation of microparticles in continuous flow. The chip integrates an active-mixing enhanced incubator and a magnetic fractionation-based separator. In the incubator, surface-functionalized magnetic beads are used to capture target particles by specific binding, which is promoted by active mixing effected by judiciously applied magnetic forces. Subsequently in the separator, the captured target particles are then separated, and thereby retrieved, in the same magnetic field. In contrast to currently existing devices that are limited by manual off-chip incubation, slow batch-mode operation, or complicated fabrication processes, our device offers automated and continuous operation with a simple structure design. The incubator and separator, as well as the chip that integrates these components, are fabricated using soft lithography techniques and systematically characterized under varying operating conditions including target to nontarget particle ratios, 1:1 and 1:10. With experimentally demonstrated reliability, flexibility and separation efficiency (>90%), the device holds great promise for sorting, purification, enrichment, and detection of cells in lab-on-chip systems.